The invention relates to a mechanical selector device for a gear changing gearbox of a motor vehicle. The invention relates more specifically to an improved selector device for controlling sequential engagement of a synchronizer clutch and a positive drive gear clutch during certain gear shift changes. The invention is especially adapted for use in gearbox systems of the type having a non-sychronized reverse gear and an axially displaceable idler gear, which is connected by means of a selector unit with a selector sliding sleeve, which sliding sleeve effects the sequential engagement of the synchronizer and drive gear clutches.
In a known selector device of this general type German Patent No. 2,603,339), the selector sliding sleeve is operated by the usual selector fork, which is connected so that it moves with an axially displaceable selector rod leading to the idler gear, which selector rod is operated by a selector finger which can, if desired, be connected to a manual gear lever. So that in the case of the reverse gear the idler gear does not have to make an ineffective movement in accompanying the axial displacement of the selector sliding sleeve necessary to engage a forward gear, the idler gear is connected to a slotted selector lever, which is pivotable about a bearing axis locationally fixed relative to the gearbox casing, which slotted selector lever has a selector slot in which a slot follower, which is connected so as to move with the selector rod, is forced to travel. The selector slot has a neutral section with a shape parallel to the axis of the selector rod--i.e., in conformity with the path of movement of the slot follower--and an adjoining selector section with a shape normal to the axis13 i.e., deviating from the path of movement. Difficulties occur with this arrangement when selecting the reverse gear because the idler gear must be brought into engagement both with a gear wheel associated with the particular gear and rotationally solidly connected to a gearbox driven shaft, which in this case is at rest, and with a gear wheel, associated with the particular gear and rotationally solidly connected to a rotating layshaft.
In order to overcome these difficulties, it has been contemplated, in the case of selector devices not of the type under consideration, in which the idler gear of the reverse gear is not connected for gear changing technical purposes to a selector sliding sleeve of a forward gear, to operate a frictionally connected synchronizer clutch of a forward gear in order to brake the layshaft over a limited part of the selection path when engaging the reverse gear. In the selector devices of German Patents No. 2,319,396 and 2,319,397, which are not of the type considered here, this takes place by means of an auxiliary cam which, at least with respect to the selection movements, is located so that it is fixed in position relative to a selector finger, which can be brought into engagement with the individual selector forks in order to operate the selector sliding sleeves and operate a selector fork of a forward gear and thus the associated synchronizer clutch during its movement from the neighboring gate position of two forward gears to the gate position of the reverse gear. In contrast, in the selector device of German Patent No. 2,506,570, which is not of the type under consideration, a first selector finger of a selector shaft is brought into engagement with a selector rod connected to the idler gear of the reverse gear, when selecting the gate position of the reverse gear, and a second selector finger of the selector shaft is brought into engagement with an auxiliary selector rod. When selecting the reverse gear, the auxiliary selector rod operates a synchronizer clutch of a forward gear.
An object of the invention consists substantially in so arranging a selector device in a gearbox system of the type mentioned above, that when selecting the reverse gear a braking action on the gearbox driving shaft ad layshaft is also obtained. This object is achieved in an advantageous manner according to the invention by providing an arrangement wherein the selector sliding sleeve is connected to a firsxt slotted selector lever pivotable about a bearing axis with fixed location relative to a gearbox casing, wherein the selector unit is connected to a first slot follower guided in a first guide slot of the first slotted selector lever and having a movement path fixed reltive to the spatial axes of the gearbox casing, the first guide slot having two neutral sections and an intermediate engagement section, wherein, in a neutral initial position of the selector unit--in which forward and reverse gears are disengaged--the neutral sections lie within and the engagement section lies outside the movement path, in such a way that when the reverse gear is selected, the first slot follower moves from one neutral section into the other neutral section, passing through the engagement section, and thus operates the synchronizer clutch exclusively and only over a limited section of the engagement path of the selector unit.
In preferred emobdiments of the invention, the idler gear is connected to a second slotted selector lever pivotable about a bearing axis fixed in location with respect to the gearbox casing and having a second guide slot, wherein the selector unit is connected to a second slot follower guided in the second slot and having a movement path fixed with respect to the spatial axes of the gearbox casing, the second slot having a neutral section and an adjoining selector section and in which, in a neutral initial position of the selector unit--in which forward and reverse gears are disengaged--the neutral section lies within and the selector section lies outside the movement path in such a way that the second slot follower is located in the area of the neutral section on selection of the forward gear and enters the selector section on selection of the reverse gear and thus displaces the idler gear, and wherein, by mutual matching of the first and second slots, the second slot follower working in conjunction with the idler gear is still located in its neutral section belonging to the initial position as long as the first slot follower, operating in conjunction with the selector sliding sleeve, is located in its appropriate engagement section.
In order to prevent undesired engagement of the synchronizing clutch during disengagement from the reverse gear, certain preferred embodiments include a spring biased clutch member mounted at the first slotted selector lever.
Further objects, features, and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.